The present invention relates to the manufacture of sealed sterile packages and more particularly to method and apparatus for detecting defects in a process for making sealed sterile packages for surgical sutures.
The foil stock for making sterile packages or containers for surgical sutures is provided on large rolls which are unwound during the feeding of the foil into the leading edge of the package making equipment. This foil stock becomes the bottom foil of the container. After cavities are formed in the bottom foil and the suture products placed therein, sheets of top foil are placed atop the bottom foil and the foils are subsequently sealed around the cavities. The facing surfaces of the foils are each coated with a thin polymeric film known as a seal coating, which facilitates sealing between the bottom foil and top foil. In the sealing operation, the seal coating melts to provide a seal between adjacent sheets of foil which are pressed together in selected areas by high temperature sealing dies.
As the foil stock or "web" comes off the source roll and is fed into the leading edge of a packaging machine, the traveling web has a tendency to "walk" in either transverse direction from the center of its longitudinal flow path through the machine. It is critical, however, that the web of foil be accurately aligned as it passes through the packaging equipment because lateral movement of the web relative to the centerline of the machine will reduce the seal margins resulting in suture packages with defective seals. This, in turn, results in significant "down time" as the process is halted to reposition the web. There is, accordingly, a need for an apparatus for maintaining alignment of the web of foil at the leading end of the packaging machine to ensure that the web is accurately positioned with respect to the centerline of the machine to increase the yield of usable foil, reduce downtime and increase product quality.
Discontinuities or voids in the polymeric seal coating on the foil occasionally occur due to imperfections in the foil manufacturing process. The presence of a discontinuity in the seal coating prevents effective sealing of the suture package, which results in product rejection. Since it is impractical to inspect the foil stock while it is on the roll, imperfectly sealed packages must be visually detected and removed following the manufacturing process, or the process must be halted whenever an imperfectly sealed package is detected so that such defective packages can be removed from the production line. This interferes with processing time and results in unnecessary processing of defective packages that must eventually be scrapped. There is, therefore, a need for an apparatus for continuously detecting seal coating imperfections in the foil stock during processing such that defective sections of the foil will not be used in the final product.
Production of sealed sterile packages for surgical sutures also requires rigorous inspection and quality control throughout the packaging process. Because of the possibility of various defects in the packaging process, and the significant cost of processing unfinished, defective products that will eventually have to be scrapped, detection of defects throughout the process is desirable to automatically identify defective products as the defects occur, and to diagnose and correct process conditions to minimize future defects. While the most significant of these inspections have heretofore been done by people, use of human operators to perform these tasks is costly and unreliable because such operators are highly susceptible to boredom and fatigue. Accordingly, there is a need for an optical inspection system which will detect defects as they occur in process and which will automatically alert the equipment operator upon detection of a particular defect so that remedial action can be taken.
The packaging equipment pulls the web of foil stock off the source roll and feeds it through a series of stations using what is known as a web advancement system. Heretofore, the web advancement system has been cam driven. The cam driven web advancement system advances the web of foil at a speed that is limited by the slow return stroke of the cam mechanism. The web advancement system moves the web from station to station and must repeatedly start and stop the web as it moves down line. Attempts to increase the speed of the cam mechanism, with resulting increased acceleration of the web, have caused web registration problems, which can result in sealing defects. Accordingly, there is a need for a web advancement system in which the overall process flow speed can be increased under controlled acceleration so that web registration problems can be minimized or eliminated.